Abstract

We report the first observation of a quasimonoenergetic electron beam emitted from a femtosecond prepulse-exploded foil. At earlier, a -thick plastic foil is irradiated by a copropagating femtosecond prepulse of modest intensity , which then explodes to become an underdense foil plasma. When a 70-fs high-intensity pulse arrives and interacts with it, a collimated electron beam of divergence angle is emitted in the forward direction. The energy spectrum of the electron beam shows a quasimonoenergetic peak at of energy spread , within which about pC of charge is contained.